1. Field of the Invention
The present invention relates to a bending device of an endoscope, which is remotely operated by a main-body operating portion to bend a curved portion provided in an insertion portion of the endoscope to be used in medical practices or the like.
2. Description of the Related Art
A related endoscope is configured so that a base end part of an insertion portion to be inserted into a body cavity is coupled to a main-body operating portion. The insertion portion has a rigid tip end portion, a bendable tube portion, and a flexible tube portion arranged in order from a tip end side. An endoscope observation section having at least an illumination portion and an observation portion is provided in the rigid tip end portion. The bendable tube portion can be bent by remote control from the main-body operating portion so as to direct the rigid tip end portion in a predetermined direction. The bendable tube portion is constituted by pivotably mounting ring-shaped bending pieces in series so as to have a joint ring structure of a predetermined length.
The bending device of the endoscope bends the bendable tube portion in an intended direction by pushing and pulling one or more operating wires inserted in the bendable tube portion. The bending device is provided in the main-body operating portion and has a manually-operated operation lever and a pulley adapted to be turned by operating the operation lever. The bending device is provided by connecting the operating wires to this pulley. Each of the operating wires is drawn out of the pulley and is fixed at a tip end thereof to a frontmost one of the bending pieces of the bendable tube portion or to the rigid tip end portion.
The flexible tube portion coupled to the bendable tube portion has flexibility in a bending direction. Thus, to prevent the operating wires from being pulled when this flexible tube portion is bent, the operating wires are inserted in flexible sleeves respectively formed of close-contact coils or the like so that each of the operating wires has an extra length. On the other hand, to prevent the followability of the bendable tube portion from being lowered when the operating lever is operated, and to surely bend the bendable tube portion in an intended direction, the operating wires are extended along the bending direction substantially without slack. Then, the flexible sleeve is provided so that a base end portion thereof is fixed in the main body operating portion, and that a tip end portion thereof is fixed to the connection portion between the flexible tube portion and the bendable tube portion. Additionally, in the bendable tube portion, a mechanism is provided, which guides the operating wires drawn out of the flexible sleeve so as not to be displaced in a circumferential direction. As described in, for example, JP-A-6-181880, a mechanism is configured by forming an inwardly-protruded lancing arch portion in the bending piece constituting the joint ring structure and then inserting the operating wires in the lancing arch portion as the mechanism for guiding the operating wires in the bendable tube portion. The lancing arch portion is formed in the bending piece by respectively providing two cuts, each of which has a predetermined length in a circumferential direction, at front and rear places on the bending piece and then causing pressure deformation in a part between these cuts from an external periphery side.
The operating wire inserted in the aforementioned lancing arch portion slides with respect to this lancing arch portion when a bending operation is performed. To smoothly operate the operating wire with a small force, it is necessary to achieve favorable slidability of this operating wire in the lancing arch portion, to minimize sliding resistance thereof, and to prevent the operating wire from being caught. Accordingly, high accuracy is required to process the lancing arch portion. Also, it is desirable to reduce the diameter of the insertion portion as much as possible so as to achieve the favorable operability to insert the insertion portion into a body cavity and to ease the pain of a subject. The reduction in the diameter of the bendable tube portion naturally results in reduction in the size of the bending piece. Thus, it is difficult to form a lancing arch portion with respect to which the operating wire inserted in the small-sized bending piece can smoothly slide. Additionally, in a case where cuts are made in the bending piece and where then, pressure deformation is caused therein, the strength of the bendable tube portion is reduced. When an external pressing force acts upon the bendable tube portions a distortion or damage may occur. Moreover, in a case where the thickness of the bending piece is increased, and where the size of the lancing arch portion is sufficiently increased, the operating wire can smoothly slide. However, in such a case, a space, in which various members are inserted cannot be assured.
Meanwhile, the operating wire is exposed from the part between the lancing arch portions placed at the front and rear places. Also, when a bending operation is performed, the operating wire is moved. Consequently, the operating wire is brought into sliding contact with another inserting member. Thus, the inserting member may be damaged. More specifically, in a case where the diameter of the insertion portion is reduced, the filling rate of the inserting members including the operating wire in the bendable tube portion is increased. Accordingly, the operating wire is moved in a state in which the operating wire is strongly pushed against another inserting member. Thus, the degree of risk of damage is further increased.